Ask the Doctors

Dear Doctor: BHT, a preservative in a lot of food products, really does a number on me. One serving of food with BHT, and I wake up with terrific pain in my head and right eye, upset stomach, chills and fever. How common are such allergies, and how can I avoid these reactions?

Dear Reader: BHA and BHT, short for butylated hydroxyanisole and butylated hydroxytoluene, are antioxidants used to preserve a wide array of foods, including snack foods, meats, butter, chewing gum and rice, as well as cosmetic products and medications. Both BHA and BHT prevent oxidation of oils, helping prevent ingredients from becoming rancid and, in some foods -- such as breakfast cereals, baked goods and potato chips -- helping maintain product crispness.

These antioxidants rarely cause allergic reactions. This was first officially evaluated more than 25 years ago in a placebo-controlled trial involving two patients who had a history of hives; the patients were first exposed to BHA and BHT via foods in their diet, then to a placebo. The elimination of these two components from their diet led to a reduction in the frequency and the severity of their hives.

In 2007, a study published in Toxicology and Applied Pharmacology identified the mechanism for the allergic reaction. In studying rats given BHT, researchers found an increase in immediate skin allergies, linking it to an allergic response that caused a type of white blood cells, known as mast cells, to release the chemicals histamine and leukotrienes. These chemicals caused an allergic response in the skin.

Questions remain, however, about the effect of the chemicals and the allergic response to them. Although the chemicals could theoretically induce nasal allergies and asthma in those already susceptible, researchers have yet to establish proof of increased asthma or nasal allergies with BHA.

BHA in particular has been singled out as potentially increasing the risk of cancer. This worry stems from studies in rats and hamsters in the 1980s. One notable study showed that rats fed diets with up to 1 to 2 percent of BHA had increased cancers of the stomach. Of those that ingested a diet with 1 percent BHA, 20 percent developed cancers of the stomach; of those that ingested a diet of 2 percent BHA, 100 percent developed cancers of the stomach.

In the United States, the highest amount of BHA that is approved in foods is 0.02 percent, which is significantly less. Overall, some studies in rats have shown an increased risk of cancer, and others have shown a decreased risk in cancer.

When it comes to humans, researchers have found little evidence of a potential cancer link. In a study published in 2000 in Food and Chemical Toxicology, researchers in the Netherlands used a dietary questionnaire to ask 120,000 men and women between the ages of 55 and 69 about their dietary intake of BHA and BHT. After six years, the authors found no increase in stomach cancer among those with higher BHA/BHT intake.

When it comes to cosmetic products, the very low percentages of BHA and BHT found in those products have not been linked to cancer.

Your reactions to BHT appear to be a form of allergy. Obviously, the best thing you can do is simply avoid this chemical. While writing this, I looked at the foods in my house to determine whether they might contain BHA or BHT and found only one item. So it seems you could eliminate your home exposure to BHA and BHT by reading labels.

Going out to eat is obviously trickier, so you'll have to be diligent. Stay away from clearly processed foods, and stick to whole, plant-based or healthful foods. Pay special attention to sauces. If a food has a sauce, make sure to ask your server if it was made from totally fresh ingredients or if it might contain foods with additives, specifically BHA or BHT.